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Bacterial blobs broadcast electrical messages to recruit other species

Deciphering interspecies signalling may lead to new means of infection control. Amy Middleton reports.

A false-colour scanning electron microscope image of plaque – a collection of microbes forming a biofilm – on a piece of floss. Bacteria in biofilms use electrical signals to 'recruit' other species to the community.

Science Photo Library / Getty Images

Think bacteria aren’t sophisticated? Think again. New research shows these microorganisms can send messages to potential new recruits in an effort to strengthen their communities known as biofilms.

These signals from within the biofilm can influence the behaviour of nearby bacteria – even those of different species – recruiting them to come and join the ranks.

“We’ve discovered that bacterial biofilm communities can actively modulate the motile behaviour of diverse bacterial species through electrical signals,” says University of California, San Diego molecular biologist Gürol Süel.

“In this way, bacteria within biofilms can exert long-range and dynamic control over the behaviour of distant cells that are not part of their communities.”

Biofilms are communities of single-celled organisms that stick to a surface using a self-produced glue-like substance – like the plaque found on our teeth.

In 2015, Süel and his team discovered that bacteria living within a biofilm can communicate with each other via electrical signals, similar to the way messages are passed on by neurons in our brains.

These signals are sent using extracellular potassium, which produces electrical waves that are broadcast through the biofilm. These signals control things such as cell metabolism and help ensure the entire biofilm gets enough sustenance to survive.

The team’s latest study, published in the journal Cell, focuses on a biofilm of Bacillus subtilis, a bacterium found in our gastrointestinal tracts, which the researchers housed in a growth chamber along with other bacterial communities.

According to the research, B. subtilis sent out potassium signals which managed to alter the membranes of cells outside their own biofilm, and even to diverse species of bacteria.

This signalling method successfully recruited Pseudomonas aeruginosa, a bacterium which can cause disease in animals and humans, into the B. subtilis biofilm.

“This electrically mediated attraction appears to be a generic mechanism that enables cross-species interactions,” the research team writes in the paper.

“Cells within a biofilm community can thus not only coordinate their own behaviour but also influence the behaviour of diverse bacteria at a distance through long-range electrical signalling.”

The work shines a light on how bacteria, including those found in our intestines, go about propagating and maintaining their communities.

“Our latest discovery suggests that the composition of mixed species bacterial communities, such as our gut microbiome, could be regulated through electrical signalling,” Süel says.

“Our work may in the future even lead to new electrical-based biomedical approaches to control bacterial behaviour and communities.”